Relative participation of the gas phase and total particulate matter in the imbalance in prostacyclin and thromboxane formation seen following chronic cigarette smoke exposure.

Chronic exposure to cigarette smoke causes an imbalance in the ratio of PGI2 and TXA2 production and is believed to favor the development of atherosclerosis. Components of the particulate phase of smoke (especially nicotine) as well as the gas phase of smoke have been shown to adversely alter arachidonic acid metabolism. To determine the relative participation of nicotine, particulate and gas phases in eliciting an imbalance in TXA2 formation, male Sprague-Dawley rats were chronically exposed (7 days/wk/mo.) to freshly generated whole smoke or gas phase from University of Kentucky Reference cigarettes and allowed access to regular drinking water or to water supplemented with nicotine (10 micrograms/ml). COHb levels were monitored to confirm smoke or gas phase inhalation. All treatment groups had lower body weights than shams. No differences in body weights were observed between smoke (+/- oral nicotine) and gas phase (+/- oral nicotine) treatment groups but all were significantly lower than oral nicotine treated animals. Platelet TXA2 production was elevated in all treatment groups compared to shams. No differences in TXA2 production were observed between smoke (+/- oral nicotine), gas phase and oral nicotine treated animals. Animals receiving gas phase/oral nicotine exhibited significantly higher platelet TXA2 production compared to the other treatments. Constituents of the gas phase as well as the particulate phase of whole smoke were both shown to elevate platelet TXA2 formation. Components of the particulate matter appear to modulate the effects of nicotine and the gas phase in the perturbation of TXA2 production in the rat smoking model.

Prostacyclin and thromboxane formation following chronic exposure to cigarette smoke condensate administered via osmotic pumps in rats. A method for chronic administration of particulates of whole smoke.

Chronic cigarette smoke exposure in vivo causes decreased conversion of [14C]arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGL2/TXA2 balance may be part of the mechanism by which smoking increases the risk of cardiovascular disease. In order to ascertain whether the particulate phase of whole smoke alone could cause these changes, rats were administered smoke condensate in propylene glycol for 56 days via two Alzet (2ML4) osmotic pumps. Pumps containing vehicle, low dose (150 micrograms/hr) or high dose (300 micrograms/hr) condensate were implanted s.c. dorsal to the thoracic vertebrae in male Sprague-Dawley rats. Three-quarters of the condensate-treated rats developed fibrin cysts encapsulating the pumps. Cysts were not seen in vehicle-treated rats. Residual pump contents were weighed and analyzed by GLC to ensure condensate delivery. No significant difference in weight gain patterns between sham-operated and treatment groups were observed. Vehicle had no effect on aortic PGI2 or platelet TXA2 formation compared to sham. Low-dose condensate was without effect on PGI2/TXA2 formation. In high-dose condensate-treated rats, PGI2 and TXA2 formation were 84% and 136%, respectively, of the vehicle control (n.s.). Pump encapsulation may be a limiting factor in the administration of complex particulate suspensions.

Alterations in prostacyclin and thromboxane formation following chronic exposure to high and low nicotine cigarettes in rats.

Chronic exposure to cigarette smoke causes an imbalance in both PGI2 and TXA2 production which is believed to favor the development of atherosclerosis. Nicotine, a major constituent of smoke, has been shown to adversely alter arachidonic acid metabolism. To determine whether varying doses of nicotine in cigarettes would influence the extent of PGI2/TXA2 alterations, male Sprague-Dawley rats were chronically exposed (7 days/wk/6 mo.) to smoke from University of Kentucky Reference cigarettes containing "low" nicotine (3A1), "high" nicotine (2R1) and "low" nicotine cigarettes spiked with enough nicotine to deliver amounts equivalent to the 2R1. COHb levels were monitored to confirm smoke inhalation. No differences in body weights were observed between treatment groups, but all were significantly lower than sham. Aortic PGI2 formation was not significantly depressed by any of the treatment groups compared to shams. Platelet TXA2 production was elevated in all treatment groups compared to shams, irrespective of nicotine content. In the rat smoking model, low nicotine cigarettes do not appear to be an advantage over higher nicotine cigarettes.

Alterations in prostacyclin and thromboxane formation by chronic cigarette smoke exposure: temporal relationships and whole smoke vs. gas phase.

Chronic cigarette smoke exposure in vivo causes decreased conversion of [14C]arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGI2/TXA2 balance may be part of the mechanism through which smoking increases the risk of cardiovascular disease. To study the influence of smoke exposure duration on this response, male rats were exposed daily to 10 puffs of freshly generated cigarette smoke. Animals were killed after 1, 4, 14, 28 and 57 days of smoke exposure and 3, 7, 14 and 28 days after cessation of the 57-day of smoke-exposure regimen. Elevated carboxyhemoglobin levels during the smoke-exposure sessions verified smoke (gas phase) inhalation. Statistically significant alterations in prostacyclin synthesis preceded those of thromboxane. A decrease of 20-25% (P less than 0.05) in PGI2 production from [14C]AA in isolated aortic tissue was found beginning 28 days after smoke was initiated and quickly rebounded when smoke exposure was terminated. Increased production of TXA2 from [14C]AA by isolated platelets became statistically significant (P less than 0.05) on the 57th day and returned to normal 7-14 days after cessation of smoke exposure. To determine the effect of gas phase constituents on the PGI2/TXA2 balance a second series of experiments divided male and female Sprague-Dawley rats into sham, whole smoke and gas phase groups. Gas phase was produced by passing whole smoke through a Cambridge filter to remove particulate matter. Per cent COHb averaged 1.4 for sham, 7.8 for whole smoke and 9.4 for gas phase groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated glucose in vivo and in vitro adversely alters prostaglandin generation in rat aortas and platelets.

An imbalance in prostacyclin (PGI2) and thromboxane (TXA2) generation from arachidonic acid (AA) may contribute to the marked increase in susceptibility to cardiovascular disease seen in diabetics. Rats made diabetic with streptozocin, and subsequently treated with saline or insulin, yielded aortic rings that synthesized decreasing amounts of PGI2 and platelets that generated increasing amounts of TXA2 in proportion to the degree of hyperglycemia. These alterations in AA metabolism were mimicked by incubating aortic rings or platelets from normal rats in buffer containing elevated glucose concentrations. Platelets incubated in elevated glucose displayed shorter times to maximal aggregation and higher percent maximal aggregation. Incubation of tissue in a buffer made hyperosmotic with mannitol had no effect on PGI2 or TXA2 formation, or platelet aggregation. These data suggest that hyperglycemia is involved in the PGI2/TXA2 imbalance and platelet abnormalities seen in diabetes, and reinforces the importance of rigid control of blood glucose as an approach to minimizing the incidence of diabetic cardiovascular complications.

Cigarette smoke exposure alters [14C]arachidonic acid metabolism in aortas and platelets of rats fed various levels of selenium and vitamin E.

Rats were placed on a basal diet supplemented with 0, 0.03, or 3 ppm selenium and 0 or 20 ppm vitamin E for 41-43 wk. Selenium deficiency decreased hepatic glutathione peroxidase activity and lowered both aortic prostacyclin (PGI2) and platelet thromboxane (TXA2) production compared to selenium- and vitamin E-supplemented animals. Vitamin E deficiency increased hepatic lipid peroxidation and decreased aortic PGI2 synthesis. Rats exposed daily for 31-32 wk to fresh smoke from a UK 2R1 reference cigarette had carboxyhemoglobin levels of 0.75 +/- 0.12 and 4.73 +/- 0.12% in sham- and smoke-exposed groups, respectively. Animals chronically exposed to cigarette smoke displayed a nearly twofold increase in pulmonary arylhydrocarbon hydroxylase activity. Smoke exposure produced a 26-33% decrease in aortic PGI2 synthesis compared to shams in the Se3E20, Se0.03E20, and Se3E0 groups. Smoking also increased platelet thromboxane 91% and 98% in the Se3E20 and Se3E0 groups compared to shams. It is concluded that cigarette-smoke exposure and selenium or vitamin E deficiency alter aortic PGI2 and platelet TXA2 production.

Increasing lipid peroxidation by vitamin E deficiency does not augment adriamycin-induced inhibition of hepatic drug metabolism.

Adriamycin treatment in vivo or addition to incubation mixtures in vitro inhibits hepatic drug metabolism. It has been suggested that adriamycin-induced membrane lipid peroxidation may be a mechanism responsible for this activity in vitro. To determine if similar mechanisms operate in vivo, adriamycin inhibition of drug metabolism was compared in rats whose tissue lipid peroxidizability was altered by manipulating dietary levels of vitamin E. Weanling rats maintained on vitamin E deficient (0 ppm) or supplemented (10 or 100 ppm) diets for 12 weeks were given either adriamycin, 5 mg/kg/week, or equal volumes of the saline vehicle for 3 weeks intraperitoneally. Vitamin E deficiency alone (0 ppm, saline pretreatment) produced a 37% increase in hepatic lipid peroxidation without any appreciable alteration in hepatic aniline hydroxylase, ethylmorphine N-demethylase or aryl hydrocarbon hydroxylase activities. Adriamycin pretreatment altered hepatic lipid peroxidizability over corresponding saline pretreated controls dependent on dietary vitamin E. No increase was seen in the 100 ppm group, while 44% and 500% increases occurred at 10 and 0 ppm vitamin E, respectively. Adriamycin pretreatment decreased drug-metabolizing enzyme activity by an average of 32% for aniline hydroxylase, 26% for ethylmorphine N-demethylase and 63% for aryl hydrocarbon hydroxylase. Statistically, decreases in drug metabolism were independent of dietary vitamin E and did not correlate with lipid peroxidizability. These data would suggest that in vivo adriamycin-induced depression of hepatic drug-metabolizing enzymes is not mediated by elevated lipid peroxidation.

The genetic activity of anthramycin, tomaymycin and sibiromycin in bacterial forward- and reverse-mutation assays and in the mouse bone-marrow micronucleus test.

The genetic activity of the structurally similar antitumor antibiotics anthramycin, tomaymycin and sibiromycin was evaluated in the standard Ames Salmonella/microsome mutagenicity assay, a Salmonella typhimurium forward-mutation assay and the micronucleus test. None of the test drugs showed any significant genetic activity in forward or reverse Salmonella mutation assays. The ability of mouse-liver enzymes to produce mutagens from the drugs was examined in the Salmonella reverse-mutation assay and was generally negative. As the concentrations of sibiromycin increased, some activity was detected in the presence of liver S-9 fractions from Aroclor-induced mice. This observation could not be verified at higher concentrations in the reverse-mutation assay due to cytotoxicity, and in the forward-mutation assay due to interference with the selection process by S-9. Cytogenetic evaluation of anthramycin and tomaymycin in the micronucleus test also gave negative results. However, significant increases in the frequency of micronucleated polychromatic erythrocytes were observed in the bone marrow of sibiromycin-treated mice. The results suggest that, except for some possible activity of sibiromycin, these drugs are generally devoid of any marked genetic activity in the test systems employed.

Impact of insulin or tolbutamide treatment on 14C-arachidonic acid conversion to prostacyclin and/or thromboxane in lungs, aortas, and platelets of streptozotocin-induced diabetic rats.

Diabetes is associated with a dramatic increase in the risk of thrombotic and atherosclerotic disease. The underlying factors responsible for this predisposition as well as the mechanisms involved have yet to be elucidated. Two endogenous substances, prostacyclin (PGI2) and thromboxane (TXA2), have recently been shown to possess significant vascular and thrombotic activity and are known to be altered in atherosclerosis, thrombotic conditions, and diabetes. We determined the conversion of 14C-arachidonic acid (AA) to PGI2 and TXA2 by lungs, aortas, and platelets obtained from chemically induced diabetic rats. In addition, we investigated the ability of insulin or tolbutamide to reverse these changes. Streptozotocin (STZ)-injected rats developed blood glucose levels 2-4 times that seen in normoglycemic controls. Intact perfused lungs isolated from rats beginning 7 days after STZ treatment synthesized 22-30% less PGI2 from 14C-AA. The ratio of PGI2/TXA2 was decreased in the diabetic rat lungs and was inversely proportional to plasma glucose levels at the time of death. Platelet TXA2 generation was increased 67% above control in diabetic rats while aortic PGI2 generation was decreased 28% below normoglycemic controls. Ten-day treatment with NPH insulin 20 U/kg s.c. in STZ-pretreated rats lowered plasma glucose toward normoglycemia more effectively than tolbutamide 200 mg/kg orally. Partial correction of the decreased pulmonary PGI2/TXA2 ratio seen in diabetic rats was produced by insulin and tolbutamide in proportion to their ability to lower blood glucose. At the doses employed, insulin caused aortic PI2 and platelet TXA2 generation from 14C-AA to approach that seen in mormoglycemic controls more effectively than tolbutamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute treatment with pyrrolo(1,4)benzodiazepine antitumor antibiotics alters in vitro hepatic drug metabolizing activity in rats.

The pyrrolo(1,4)benzodiazepine antitumor antibiotic, anthramycin, shares a number of toxicities with the widely used anticancer agent adriamycin. We investigated whether acute doses of anthramycin and the structurally related compounds, sibiromycin and tomaymycin, would depress P-450-dependent drug biotransformations as has been reported for adriamycin. Alterations in drug metabolism rates were determined in rats using 50 and 75% of the approximate 7-day LD50 determined in mice. 4 days post dosing ethylmorphine demethylase and aniline hydroxylase activities in liver 9000 g supernatant were depressed from 26 to 76%. Tomaymycin lowered drug metabolism in a dose-related manner, while sibiromycin produced the greatest amount of depression. Like adriamycin, the pyrrolo(1,4)benzodiazepines possess the ability to depress hepatic drug metabolism and therefore may affect the disposition of compounds with which they are co-administered.

Chronic cigarette smoke exposure adversely alters 14C-arachidonic acid metabolism in rat lungs, aortas and platelets.

Male rats were exposed to freshly generated cigarette smoke once daily, 5 times a week for 10 weeks. Inhalation of smoke was verified by elevated carboxyhemoglobin in blood sampled immediately after smoke exposure and by increased lung aryl hydrocarbon hydroxylase activity 24 hours after the last smoke exposure. Aortic rings isolated from smoke-exposed rats synthesized less prostacyclin (PGI2) from 14C-arachidonic acid than rings from sham rats. Platelets from smoke-exposed rats synthesized more thromboxane (TXA2) from 14C-arachidonic acid than platelets from room controls but not those from sham rats. Lung microsomes from smoke-exposed rats synthesized more TXA2 and had a lower PGI2/TXA2 ratio than lung microsomes from room controls and shams. It is concluded that chronic cigarette smoke exposure alters arachidonic acid metabolism in aortas, platelets and lungs in a manner resulting in decreased PGI2 and increased TXA2, thereby creating a condition favoring platelet aggregation and a variety of cardiovascular diseases.

Metabolism of isosorbide dinitrate in the isolated perfused rabbit lung.

The uptake and metabolism of isosorbide dinitrate was investigated in the recirculating isolated perfused rabbit lung and in lung homogenate 9000 X g supernatant. Concentration versus time profiles from the isolated lung experiments indicate rapid metabolism of isosorbide dinitrate and corresponding increases in the metabolites 5-isosorbide mononitrate, 2-isosorbide mononitrate, and isosorbide. The data suggest that the mononitrates formed in the lung tissue were converted to isosorbide at an extraordinarily high rate. Surprisingly, the rate of appearance of completely denitrated isosorbide was greater when isosorbide dinitrate was administered to the lung than when the mononitrate metabolites of isosorbide dinitrate were administered. The results suggest rapid metabolism of a substantial portion of the mononitrates formed endogenously from isosorbide dinitrate before partitioning of mononitrates into the perfusion medium could occur. The metabolism of isosorbide dinitrate in lung homogenate 9000 X g supernatant exhibited a metabolic scheme kinetically different from the intact lung studies, as isosorbide was formed slowly from a mononitrate intermediate and not by a near-simultaneous cleavage of both nitrate ester groups. Intravascular multiple-dose studies did not demonstrate any inhibition between isosorbide dinitrate and the mononitrates.

Lung, aorta, and platelet metabolism of 14C-arachidonic acid in vitamin E deficient rats.

14C-arachidonic acid metabolism was determined in aortas, platelets, and perfused lungs from rats pair fed a basal diet supplemented with 0 or 100 ppm vitamin E for 11 weeks. Spontaneous erythrocyte hemolysis tests showed 92% and 8% hemolysis for the 0 and 100 ppm vitamin E groups, respectively. Elevated lung homogenate levels of malonaldehyde in the 0 ppm group confirmed its deficient vitamin E status. Aortas from the vitamin E deficient group synthesized 54% less prostacyclin than aortas from the supplemented group (p less than 0.05). Although thromboxane generation by platelets from the vitamin E deficient group exhibited a 37% increase, this difference was not statistically significant compared to the supplemented animals. Greater amounts of PGE2, PGF2 alpha, TXB2, and 6-keto-PGF1 alpha were obtained in albumin buffer perfusates from lungs of vitamin E deficient rats than in those from supplemented rats. Significant differences (p less than 0.05) were noticed, however, only for PGE2 and PGF2 alpha. These studies indicate that vitamin E quantitatively alters arachidonic acid metabolism in aortic and lung tissue but its effect on thromboxane synthesis by platelets is less marked.

Influence of pretreatment with tobacco smoke condensate or 3-methylcholanthrene on [14C] benzo (a) pyrene metabolism in the isolated perfused rabbit lung.

Pretreatment 24 h before sacrifice with i.p. tobacco smoke condensate (TSC) or 3-methylcholanthrene (3MC) increased the rate of disappearance of [14C]benzo(a)pyrene (BP) from an isolated perfused rabbit lung model. Both pretreatments significantly increased the amount of most metabolites formed. This study indicates that rabbits tend to resemble rats, mice and hamsters in that increased rates of pulmonary BP metabolism are a consequence of exposure to TSC.

Protection against anthramycin-induced toxicity in mice by coenzyme Q10.

Pretreatment of Swiss Webster mice with coenzyme Q10 (CoQ) markedly reduced the lethality of the antitumor antibiotic anthramycin as well as its ability to decrease ventricular weights. In tumor-bearing mice CoQ pretreatment did not produce any consistent alteration of radioactivity levels in blood, heart, tumor, lungs, kidneys, liver, muscles, brain, or spleen after [15-3H]anthramycin administration. Gross alterations in anthramycin distribution is probably not the mechanism by which CoQ alters the cardiotoxicity and lethality of anthramycin.

Acute tobacco smoke exposure alters the profile of metabolites produced from benzo[alpha]pyrene by the isolated perfused rabbit lung.

The influence of whole tobacco smoke or the gas phase from smoke on the metabolism of [14C]benzo[alpha]pyrene was examined using the isolated perfused rabbit lung model. Fresh whole tobacco smoke mixed with the air ventilating the perfused lung produces an immediate and dose related decrease in the metabolism of [14C]benzo[alpha]pyrene. The metabolites of [14C]benzo[alpha]pyrene, diols, quinones, phenols and polar compounds are generally decreased in quantity. At the lowest level of smoke administered the percentage of BP-7,8-diol produced is increased dramatically. The results indicate that one of the factors contributing to the carcinogenicity of tobacco smoke may be its ability to produce an immediate alteration in the pulmonary metabolism of polycyclic aromatic hydrocarbons.